Atomic Theory Timeline

Major World Events

  • Trojan War (900-600 BC)
  • Battle of Thermoeylae (480 BC)
  • Birth of Jesus Christ (8-2/29-36 BC)

  • Crusades (1095-1291)
  • The Enlightenment (1700’s)
  • United States Declaration of Independence Signed (1776)

  • Industrial Revolution (1800’s)
  • The Alamo (1836)
  • American Civil War (1861-1865)

  • Battle of Agurdat (1875)
  • Russo-Turkish War (1877-1878)
  • Battle of Adowa, Ethiopia (1896)

  • Russo-Japanese War/ Bloody Sunday (1905)
  • Albert Einstein Revolutionizes physics (1905)
  • Panama Canal opens (1914)

  • World War I (1914-1918)
  • United States Stock Market Crashes/Global Depression (1929)
  • World War II (1939-1945)

  • Cuban Missile Crisis (1962)
  • Neil Armstrong Landed on the Moon (1969)
  • Terrorists Attacked the United States (9/11-2001)

Ancient Greeks and Romans

Leucippus - A Greek philosopher who was born and presumably died in the 1st half of the 500's BC, in Miletus or Abdera, Greece. He was among the earliest philosophers of atomism, the idea that everything is composed entirely of various imperishable, indivisible elements called atoms.

external image atom_model_03_FF.gifAs early at the 5th century B.C, Greek philosophers like Leucippus and Democritus have suggested the existence of imperishable, indivisable elements called atoms. This is the basic model of a basic atom.

Democritus - A pre-Socratic Greek philosopher, who was born in Greece in the year 460 B.C. and died in 370 B.C.
He was a student of Leucippus and co-originator of the belief that all matter is made up of various imperishable, indivisible elements which he called atoma, or indivisible units, a.k.a the atom.


Aristotle - A Greek philosopher and a student of Plato. He was born in Greece in 384 BC and died in March of 322 BC. He founded the five main elements. They were fire, earth, air, water and aether. They each have there own meaning. Aether is all the stars, plants and heavens.



Antoine Lavoisier – Born in Paris, France on August 26, 1743 and died on May 8, 1794 by being beheaded at the height of the French Revolution. He was called the “father of modern chemistry”. Lavoisier made multiple contributions to the world of chemistry between 1770 and 1790. He stated the first Law of the Conservation of Mass. He also named oxygen in 1778 and named hydrogen in 1783 as elements. This lead to Lavoisier creating the first ever Periodic Table of Elements. Also in these years, he introduced the metric system.

Joseph Priestly – A natural philosopher born in England on March 26, 1733 and died on February 8, 1804. From 1774 to 1780, Priestly conducted research experiments on air that led to his discovery of oxygen. Priestly also made connections between oxygen and respiration.

Charles-Augustin de Coulomb – A physicist born in France on June 14, 1736 and died on August 23, 1806. From 1779 to 1785 Coulomb conducted research experiments that led him to discovering Coulomb’s Law. Coulomb’s Law states that the magnitude of the electrostatic force between electric charges is directly proportional to the product of the magnitudes and inversely proportional the square of the distance between the charges.
27946.jpg 230px-Charles_de_coulomb.jpg


John Dalton – Born in England on September 6, 1766 and died on July 27, 1844, Dalton was a chemist, meteorologist, and physicist. From 1800 to 1805, Dalton did research that would led to the development of the atomic theory. He also created Dalton’s Law, which is about water absorbing gasses and partial pressures.
Five main points of Dalton's Atomic Theory:
  • Elements are made of tiny particles called atoms
  • All atoms of a given element are identical
  • The atoms of a given element are different from those of any other element
  • Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms.
  • Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.


Jons Jakob Berzelius – A chemist born in Sweden on August 20, 1779 and died on August 7, 1848. Along with Dalton and Lavoisier, he is considered one of the “fathers of chemistry.” From 1828 to 1833, Berzelius compiled a table of relative atomic weights and stated that elements are built up from atoms of hydrogen. In this time he also identified silicon, selenium, thorium, and cerium.

William Crookes – A chemist and physicist born in England on June 17, 1832 and died April 4, 1919. In 1861, Crookes discovered an element with a bright green emission line in its spectrum, naming it Thallium. In 1895, Crookes discovered helium. He invented the Crookes’ radiometer, and also the Crookes tube to study canal rays. In 1871 Crookes also published many papers on spectroscopy.


Wilhelm Roentgen – A physicist born in Prussia on March 27, 1845 and died on February 10, 1923. On November 8, 1895, Roentgen produced and detected electromagnetic radiation in a wavelength range, presently known as X-Rays.

J.J. Thomson – Was born in the United Kingdom, on December 18, 1856 and died on August 30, 1940. In 1897, Thomson was credited for the discovery of the electron and of isotopes, the proposition of the plum pudding model of the atom, and the invention of the mass spectrometer.
Plum-Pudding Model
Plum-Pudding Model
The plum pudding model was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is made up of electrons, surrounded by a soup of positive charge to balance the electron's negative charge, like plums surrounded by pudding. The electrons were thought to be positioned throughout the atom, but with many structures possible for positioning multiple electrons, particularly rotating rings of electrons. Instead of a soup, the atom was also sometimes said to have had a cloud of positive charge.

Henri Becquerel – A physicist born in France on December 15, 1852 and died on August 25, 1908. In 1896, Becquerel accidentally discovered the spontaneous emission of nuclear radiation by wrapping fluorescent material in photographic plates and finding them fully exposed after being locked in a closet for multiple days. In 1898, Becquerel and his wife Marie Curie studied radioactive materials, like pitchblende (the ore from which uranium is extracted.) These studies led to Curie and Becquerel releasing an article proclaiming their discovery of the element Polonium. In late December of 1898, they announced the existence of a second element, Radium.

Marie Curie – A physicist and chemist born in Poland on November 7, 1867 and died on July 4, 1934. In 1898, Curie and her husband Henri Becquerel studied radioactive materials, like pitchblende (the ore from which uranium is extracted.) These studies led to Curie and Becquerel releasing an article proclaiming their discovery of the element Polonium. In late December of 1898, Curie announced the existence of a second element, Radium.


Ernest Rutherford – A nuclear physicist born in New Zealand on August 30, 1871 and died on October 19, 1937. Rutherford became known as the “father” of nuclear physics. From 1900 to 1903, Rutherford researched the transmutation of elements. In this time, Rutherford discovered the “half-life” of a sample of radioactivity. In 1907, he conducted the experiments that discovered the nuclear nature of atoms. His interpretation of this experiment led him to the Rutherford model of the atom having a very small positively charged nucleus orbited by electrons. He was the first scientist to transmute one element into another at the time he converted nitrogen into oxygen. He is also responsible for the “gold-foil” experiment.
Planetary Model
Planetary Model
In 1911, Rutherford performed his Geiger-Marsden experiment and found fault in the Plum-Pudding Model. Rutherford's new atom model had multiple essential modern features, including a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom. This atomic model resembles a solar system.

Robert Andrews Millikan – A physicist born in the United States on March 22, 1868 and died on December 19, 1953. From 1909 to 1913, Millikan experimented with charges and was successful in measuring the charge on an electron. In later years, Millikan did work on the “photoelectric effect” and cosmic rays.

Albert Einstein – A theoretical physicist born in Germany on March 14, 1879 and died on April 18, 1955. In 1910, he wrote a paper that described the effect of light scattered by individual molecules in the atmosphere, answering the question “why the sky is blue.” In 1911, he published a paper about the effects of gravity on light, the gravitational redshift and the gravitational deflection of light. It helped astronomers discover ways of detecting the deflection during a solar eclipse. In 1915, Einstein published his General Theory of Relativity, which explains gravitation as distortion of the structure of space-time by matter, affecting the inertial motion of other matter.
- (His later-year contributions include relativistic cosmology, capillary action, critical opalescence, classical problems of statistical mechanics and their connection to quantum theory, an explanation of the Brownian movement of molecules, atomic transition probabilities, the quantum theory of a monatomic gas, thermal properties of light with low radiation density, a theory of radiation, the conception of a unified field theory, and the geometrization of physics. All of these discoveries took place sometime between 1915 and 1930.)


Niels Bohr – A physicist born in Denmark on October 7, 1885 and died on November 18, 1962. In 1913, Bohr published his model of atomic structure, which introduced the theory of electrons traveling in orbits around the atom's nucleus. It also stated that the chemical properties of the element were determined greatly by the number of electrons in the outer orbits. In 1927, he and Werner Heisenberg formulated the Copenhagen interpretation of quantum mechanics.
Rutherford-Bohr Model
Rutherford-Bohr Model
Introduced in 1913 by Niels Bohr, is an improvement of Rutherford's planetary model.
This model depicts the atomas a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus — similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. This model is a quatum-physics based modification.

Werner Heisenberg A physicist born in Germany on December 5, 1901 and died on February 1, 1976. In 1925, Heisenberg invented matrix mechanics, which was the first form of quantum mechanics. In 1927, Heisenberg created his renowned “Uncertainty Principle”, and worked with Neils Bohr to formulate the Copenhagen interpretation of quantum mechanics.
Werner Heisenberg
Electron-Cloud Model
Electron-Cloud Model
In the 1920's, Werner Heisenberg and Erwin Schrodinger developed probability functions to determine the reigions (clouds) in which electrons would probably be found in an atom.

James Chadwick A physicist born in England on October 20, 1891 and died on July 24, 1974. In 1932, Chadwick discovered that the particle in the nucleus of an atom, later dubbed the “neutron”, has no electric charge.

Erwin Schrodinger A physicist born in Austria-Hungary on August 12, 1887 and died on January 4, 1961. In early 1926, Schrodinger published a paper on wave mechanics and what is presently known as “The Schrodinger Equation”, which describes the space and time dependence of quantum mechanical systems. Later, in 1940, Schrodinger wrote around 50 publications on various topics, including the unified field theory. In 1944 he wrote “What is Life?”, a book about Negentropy and the concept of a complex molecule with the genetic code for living organisms.
Erwin Schrodinger


  1. Arnold Thackray, John Dalton: Critical Assessments of His Life and Science, Harvard University Press, (1972) ISBN 0-674-47525-9
  2. DM Hunt, KS Dulai, JK Bowmaker, JD Mollon, "The Chemistry of John Dalton's Color Blindness", Science, February 17, 1995
  3. Lindsay, Jack, ed. Autobiography of Joseph Priestley. Teaneck: Fairleigh Dickinson University Press, 1970. ISBN 0838678310
  4. Miller, Peter N., ed. Priestley: Political Writings. Cambridge: Cambridge University Press, 1993. ISBN 0521425611.
  5. Passmore, John A., ed. Priestley's Writings on Philosophy, Science and Politics. New York: Collier Books, 1964.
  6. Rutt, John T., ed. Collected Theological and Miscellaneous Works of Joseph Priestley. 2 vols. London: George Smallfield, 1832.
  7. Rutt, John T., ed. Life and Correspondence of Joseph Priestley. 2 vols. London: George Smallfield, 1831.
  8. Schofield, Robert E., ed. A Scientific Autobiography of Joseph Priestley (1733–1804): Selected Scientific Correspondence. Cambridge: MIT Press, 1966
  9. Goodstein, D., "In defense of Robert Andrews Millikan", Engineering and Science, 2000. No 4, pp30-38 (pdf).
  10. Millikan, R A (1950) The Autobiography of Robert Millikan
  11. Nobel Lectures, "Robert A. Millikan – Nobel Biography". Elsevier Publishing Company, Amsterdam.
    • David C. Cassidy, "Uncertainty: The Life and Science of Werner Heisenberg", (W. H. Freeman) ISBN 0-7167-2503-7
    • James Glanz, "New Twist on Physicist's Role in Nazi Bomb". The New York Times, February 7, 2002.
    • Mark Walker, German National Socialism and the Quest for Nuclear Power, 1939-1949 (London: Cambridge University Press, 1990). ISBN 0-521-36413-2 (Hardcover) ISBN 0-521-43804-7 (Paperback)
    • Thomas Powers. Heisenberg's War: The Secret History of the German Bomb (Knopf) ISBN 0-394-51411-4(Hardcover) ISBN 0-316-71623-5(Paperback)
    • Paul Lawrence Rose. Heisenberg and the Nazi Atomic Bomb Project, 1939-1945: A Study in German Culture. University of California Press, 1998, ISBN 0-520-21077-8
    • Heisenberg, Werner. Across the frontiers ; translated from the German by Peter Heath. (Ox Bow Press, 1990) ISBN 0-918024-80-3 (Hardcover) ISBN 0-918024-81-1 (Paperback)
  12. Hellemans, Alexander; Bryan Bunch (1988). The Timetables of Science. New York, New York: Simon and Schuster, 411. ISBN 0671621300.
    • Dahl, Per F., "Flash of the Cathode Rays: A History of J.J. Thomson's Electron". Institute of Physics Publishing. June, 1997. ISBN 0-7503-0453-7
  13. Reid, Robert William (1974). Marie Curie. London: Collins, page 19. ISBN 0-00-211539-5.
  14. Bailey C. (1928) The Greek Atomists and Epicurus. Oxford
  15. Bakalis Nikolaos (2005) Handbook of Greek Philosophy: From Thales to the Stoics Analysis and Fragments, Trafford Publishing, ISBN 1-4120-4843-5
  16. Barnes J. (1982) The Presocratic Philosophers, Routledge Revised Edition
  17. Burnet J. (2003) Early Greek Philosophy, Kessinger Publishing
  18. Guthrie W. K. (1979) A History of Greek Philosophy – The Presocratic tradition from Parmenides to Democritus, Cambridge University Press.
  19. Kirk G. S., Raven J. E. and Schofield M. (1983) The Presocratic Philosophers, Cambridge University Press, Second edition.
  20. Melchert, Norman (2002). The Great Conversation: A Historical Introduction to Philosophy. McGraw Hill. ISBN 0-19-517510-7.
  21. Neill, Alex; Aaron Ridley (1995). The Philosphy of Art: Readings Ancient and Modern. McGraw Hill, 488.
  22. Jones, W.T. (1980). The Classical Mind: A History of Western Philosophy. Harcourt Brace Jovanovich, 216. , cf. Vita Marciana 41.